1. Field of the Invention
The present invention relates generally to a hierarchical memory mapping system and more particularly relates to a system that provides hierarchical table lookups for mapping across a multiprotocol messaging environment
2. Description of the Background
With tie explosive increase of traffic on the Internet, specifications standardizing the transfer of electronic messages are frequently being developed. For example, RFC 1327 specifies a standard mechanism for mapping between X.400 and Simple Mail Transfer Protocol (SMTP). Every mail gateway between X.400 and SMTP must follow this specification. One important aspect of this mapping involves the mapping of addresses. To facilitate the mapping of addresses, RFC 1327 specifies three global tables for maintaining equivalences between X.400 domain names and Internet domain names. The three tables are rfc2or, or2rfc and rfc1148gate. The rfc2or table maps Internet domain names into their equivalent X.400 O/R domains. The or2rfc table maps X.400 O/R domains into their equivalent Internet domain names. The rfc1148gate table maps Internet domain names to their preferred gateway name. The three tables are regularly updated by global naming authorities. Every name, whether it be an originator name, a recipient name or any type of copy name, is looked up in at least one of these tables.
The RFC 1327 specification requires that the best matching table entry, if any, be used. The best match is considered to be the longest matching domain name, according to that domain's hierarchy. Typically, this means that each name is looked up with its full domain name as the key. If that lookup fails, the domain is shortened by one element, a subdomain, and looked up again. This repeats until a matching entry is found, or there are no more subdomains. With thousands of entries in each mapping table, this process of a linear search throughout one or more global tables becomes burdensome, time-consuming and expensive. These costs are compounded by the fact that every address on every e-mail item must undergo these lookups. Furthermore, many addresses never match any table entries, thus amounting to wasted work.